JP2008135441A - Two-dimensional photonic crystal surface-emitting laser and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-dimensional photonic crystal surface-emitting laser capable of increasing light extraction efficiency in a main light emission direction, and to provide a method of manufacturing the two-dimensional photonic crystal surface-emitting laser easily. <P>SOLUTION: The two-dimensional photonic crystal surface-emitting laser has an active layer 2, guide layers 3, 4, and cladding layers 5, 6. The cladding layer 6 includes a photonic crystal period structure 10a arranged two-dimensionally. The photonic crystal period structure 10a is composed of solid materials 11a, 11b that are arranged along the emission direction of emission light L1 and have a different refractive index, thus enabling more light to be subjected to primary diffraction in the emission direction of the emission light L1. The emission light L1 is utilized as surface light emission, thus obtaining not less than 50% efficiency in using light. More specifically, the light extraction efficiency can be increased in the main light emission direction. Also, the two-dimensional photonic crystal surface-emitting laser can be manufactured without bonding substrates each other as before. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a two-dimensional photonic crystal surface emitting laser and a method of manufacturing the same, and more particularly, to a photonic crystal periodic structure that is two-dimensionally arranged in the vicinity of an active layer that emits light by carrier injection. The present invention relates to a two-dimensional photonic crystal surface emitting laser that resonates with a crystal and emits surface light, and a manufacturing method thereof.

  Conventionally, various surface emitting lasers that emit laser light perpendicularly from a substrate surface have been developed and studied. Surface-emitting lasers can integrate (array) many elements on the same substrate, and coherent light is emitted in parallel from each element, so in the fields of parallel optical pickup, parallel optical transmission, and optical parallel information processing Applications are expected.

  Conventionally, a two-dimensional photonic crystal surface emitting laser using a photonic crystal has been proposed as a surface emitting laser (see, for example, Patent Document 1). A photonic crystal is a crystal having a refractive index period that is comparable to or smaller than the wavelength of light. A two-dimensional photonic crystal surface emitting laser has a photonic crystal periodic structure arranged two-dimensionally in the vicinity of an active layer that emits light by carrier injection, and resonates with a photonic crystal to emit surface light. is there.

  In the two-dimensional photonic crystal surface emitting laser proposed in Patent Document 1, the photonic crystal periodic structure is formed in a cylindrical shape, an elliptical column shape, or a rectangular column shape. FIG. 14 is a schematic cross-sectional view showing an example of the configuration of a conventional two-dimensional photonic crystal surface emitting laser. As shown in FIG. 14, the cross-sectional shape in the direction perpendicular to the substrate surface of the photonic crystal periodic structure 110a is a quadrangular shape. In this case, the light by the first-order diffraction is divided into the outgoing light L1 upward and the outgoing light L2 downward with the same intensity (50% and 50%). The light used as the laser light is one of the outgoing lights L1 and L2. For this reason, there has been a problem that the utilization efficiency of surface-emitting light is low.

Thus, studies are being conducted to increase the utilization efficiency of surface-emitting light to 50% or more. FIG. 15 is a schematic cross-sectional view showing another example of the configuration of a conventional two-dimensional photonic crystal surface emitting laser. As shown in FIG. 15, a two-dimensional photonic crystal surface emitting laser is proposed in which the width of the cross-sectional shape in the direction perpendicular to the substrate surface of the photonic crystal periodic structure 110b is gradually reduced along the main light emitting direction ( For example, see Patent Document 2).
JP 2000-332351 A JP 2003-273455 A

  In the two-dimensional photonic crystal surface emitting laser proposed in Patent Document 2, the main light emitting direction (for example, in FIG. 15, from the substrate side to the active layer side) is obtained by setting the shape of the photonic crystal periodic structure to a conical shape or the like. The light extraction efficiency in the normal direction of the substrate surface toward the substrate and in the emission direction of the emitted light L1 is increased. However, it is difficult to form a conical shape. For example, a thin cylinder can be produced by a method of forming in multiple stages while changing the diameter, but in this case, an exposure process is required according to the number of the multiple stages, and the number of processes increases, and the substrate If the method of sticking together is not used, production is difficult. Therefore, there are problems that the manufacturing process is complicated and many, and that alignment is difficult.

  Therefore, the main object of the present invention is to increase the light extraction efficiency in the main light emission direction and the two-dimensional photonic crystal surface emitting laser capable of increasing the light extraction efficiency in the main light emission direction. It is to provide an easy manufacturing method of a two-dimensional photonic crystal surface emitting laser.

  The two-dimensional photonic crystal surface emitting laser according to the present invention includes an active layer that emits light by carrier injection. In addition, a guide layer for confining the emitted light in the active layer is provided. A cladding layer for injecting carriers into the active layer is also provided. The active layer is disposed so as to be sandwiched between the guide layer and the clad layer. The guide layer or the clad layer includes a two-dimensionally arranged photonic crystal periodic structure. The photonic crystal periodic structure is composed of two or more kinds of solid materials having different refractive indexes arranged along the emission direction of the emitted light emitted from the two-dimensional photonic crystal surface emitting laser.

  In this case, the light leaking from the active layer is amplified by second-order diffraction (resonance) by the photonic crystal periodic structure, and surface light is emitted from the cladding layer by the first-order diffraction. Two or more kinds of solid materials constituting the photonic crystal periodic structure have a refractive index smaller than that of the guide layer and the cladding layer. Two or more kinds of solid materials have different refractive indexes and are arranged along the emission direction of the emitted light. Therefore, although the photonic crystal periodic structure has a cylindrical shape, the refractive index felt by the light in the laser is inclined, so that the light is first-order diffracted more in a specific direction. Therefore, by using the light that is first-order diffracted in the direction as the surface emission, a light use efficiency of 50% or more can be obtained. That is, the light extraction efficiency in the main light emission direction can be increased.

  Preferably, two or more kinds of solid materials are arranged in an ascending or descending order of refractive index. In this case, the gradient of the refractive index of the photonic crystal periodic structure can be given in a specific direction. For example, a direction from a solid material having a lower refractive index toward a solid material having a higher refractive index can be a main light emitting direction.

  The manufacturing method of the two-dimensional photonic crystal surface emitting laser according to the present invention includes a step of preparing a substrate. Moreover, the process of laminating | stacking a 1st semiconductor layer on the surface of a board | substrate is provided. Also, a photonic composed of two or more kinds of solid materials having different refractive indexes arranged along the emission direction of the emitted light emitted from the two-dimensional photonic crystal surface emitting laser on the surface of the first semiconductor layer. Forming a periodic crystal structure. In addition, a step of laminating the second semiconductor layer on the surface of the first semiconductor layer so as to embed the photonic crystal periodic structure is provided. Moreover, the process of forming an electrode is provided.

  In this case, it is possible to increase the light extraction efficiency in the main light emitting direction by constructing the refractive index distribution by forming the photonic crystal periodic structure from two or more solid materials having different refractive indexes. A two-dimensional photonic crystal surface emitting laser can be manufactured. According to this manufacturing method, a two-dimensional photonic crystal surface emitting laser can be manufactured by sequentially stacking semiconductor layers on one surface of a single substrate. There is no need to use a method of pasting together. Therefore, the manufacturing process can be simplified, and as a result, the manufacturing cost of the two-dimensional photonic crystal surface emitting laser can be reduced.

  Preferably, the step of forming the photonic crystal periodic structure includes a step of forming one solid material. Moreover, the process of apply | coating a resist on the surface of one solid material is included. Moreover, the process of forming a hole in a resist is included. Further, it includes a step of depositing another solid material inside the hole. Moreover, the process of removing a resist is included. Further, the method includes a step of partially removing the exposed one solid material using another solid material remaining at the position inside the hole as a mask. According to this manufacturing method, a two-dimensional photonic crystal surface emitting laser can be manufactured by sequentially laminating semiconductor layers on one surface of one substrate without bonding the substrates together.

  Preferably, the step of forming the photonic crystal periodic structure includes a step of applying a resist on the surface of the first semiconductor layer. Moreover, the process of forming a hole in a resist is included. Moreover, the process of laminating | stacking one solid material and another solid material in order inside a hole is included. Moreover, the process of removing a resist is included. According to this manufacturing method, a two-dimensional photonic crystal surface emitting laser can be manufactured by sequentially laminating semiconductor layers on one surface of one substrate without bonding the substrates together.

  As described above, the two-dimensional photonic crystal surface emitting laser of the present invention can increase the light extraction efficiency in the main light emitting direction. Further, according to the method for manufacturing a two-dimensional photonic crystal surface emitting laser of the present invention, it is possible to easily manufacture a two-dimensional photonic crystal surface emitting laser capable of increasing the light extraction efficiency in the main light emitting direction. it can.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing the configuration of the two-dimensional photonic crystal surface emitting laser according to the first embodiment. As shown in FIG. 1, the two-dimensional photonic crystal surface emitting laser includes a substrate 1. In the normal direction of the surface of the substrate 1, the emitted light emitted to one surface side of the substrate 1 is indicated by L 1 and the emitted light emitted to the other surface side of the substrate 1 is indicated by L 2. In this case, the emitted light L1 is light having a higher intensity than the emitted light L2. Hereinafter, the direction in which light having a higher intensity is emitted, that is, the surface of the two-dimensional photonic crystal surface emitting laser on the main light emitting direction side is referred to as a main surface.

  A first semiconductor layer 21 is stacked on the main surface side on the surface of the substrate 1. The first semiconductor layer 21 includes an active layer 2 that emits light by injection of carriers (that is, electrons and holes), a lower guide layer 3 and an upper guide layer 4 that confine the emitted light in the active layer 2, and an active layer 2. The lower clad layer 5 for injecting carriers is constituted. In the first semiconductor layer 21, the lower cladding layer 5, the lower guide layer 3, the active layer 2, and the upper guide layer 4 are laminated in this order from the substrate 1 side to the main surface side. The active layer 2 is disposed so as to be sandwiched between the lower guide layer 3 and the upper guide layer 4.

  On the main surface side of the surface of the first semiconductor layer 21, the photonic crystal periodic structure 10 a is two-dimensionally arranged along the direction in which the surface extends. The photonic crystal periodic structure 10a is composed of two types of solid materials 11a and 11b having different refractive indexes. The solid materials 11a and 11b are arranged along the emission direction of the emitted light L1 emitted from the two-dimensional photonic crystal surface emitting laser. In this case, the refractive index of the solid material 11a is smaller than the refractive index of the solid material 11b. That is, the two kinds of solid materials 11a and 11b are arranged and arranged in ascending order of refractive index from the substrate 1 side to the main surface side. The direction from the solid material 11a having a lower refractive index toward the solid material 11b having a higher refractive index is the main light emitting direction, and outgoing light L1 having higher intensity is emitted.

  In addition, the second semiconductor layer 22 is stacked on the surface on the main surface side of the first semiconductor layer 21 so as to embed the photonic crystal periodic structure 10a. The second semiconductor layer 22 includes an upper cladding layer 6 for injecting carriers into the active layer 2 and a contact layer 7. In the second semiconductor layer 22, the upper cladding layer 6 and the contact layer 7 are laminated in this order from the substrate 1 side to the main surface side. The active layer 2 is disposed so as to be sandwiched between the lower cladding layer 5 and the upper cladding layer 6.

As the solid material 11a constituting the photonic crystal periodic structure 10a, for example, SiO ₂ can be used, and the refractive index of SiO ₂ is about 1.45. For example, Al ₂ O ₃ can be used as the solid material 11b, and the refractive index of Al ₂ O ₃ is about 1.76. The refractive indexes of the solid materials 11a and 11b may be smaller than the refractive indexes of the guide layer and the cladding layer. Therefore, for example, AlGaN (aluminum gallium nitride), GaN (gallium nitride) or the like can be employed as the guide layer and the cladding layer, and the refractive index thereof is about 2.5.

  The upper electrode 9 is formed on the main surface side surface of the second semiconductor layer 22. That is, the contact layer 7 is provided as a layer for connecting the upper cladding layer 6 and the upper electrode 9. The upper electrode 9 can be an anode electrode, and can be formed into, for example, a cylindrical shape or a polygonal column shape. The surface on the main surface side of the second semiconductor layer 22 where the upper electrode 9 is not formed functions as a light emission region. The planar outer shape of the upper electrode 9 can be, for example, a polygonal shape that matches a two-dimensional photonic crystal described later. A lower electrode 8 is formed over the entire surface of the substrate 1 opposite to the main surface. The lower electrode 8 can be a cathode electrode. The lower electrode 8 and the upper electrode 9 can be gold (Au) based electrodes. The material is not limited to this material, and a conductive material transparent to the light generated in the active layer 2 can also be used.

  The active layer 2 can be made of a single semiconductor material, for example. Further, for example, the active layer 2 can have a multiple quantum well structure using a semiconductor material such as GaN / InGaN. That is, the active layer 2 can have a plurality of light emitting portions that emit light when carriers are injected, and a separation portion that is provided so as to separate the plurality of light emitting portions. As described above, a double heterojunction is formed by sandwiching the active layer 2 between the lower guide layer 3 and the upper guide layer 4 so that carriers are confined in the active layer 2 and carriers contributing to light emission are concentrated in the active layer 2. It has become. By applying a voltage between the lower electrode 8 and the upper electrode 9, the active layer 2 emits light, and light leaked from the active layer 2 enters the two-dimensional photonic crystal formed by the photonic crystal periodic structure 10a.

  The photonic crystal periodic structure 10a is, for example, arranged at each apex of two-dimensionally spread squares on the surface on the main surface side of the first semiconductor layer 21 to form a known two-dimensional photonic crystal. . That is, the distance between one photonic crystal periodic structure 10a and the four adjacent photonic crystal periodic structures 10a closest to the photonic crystal periodic structure 10a has the same value (lattice spacing of the two-dimensional photonic crystal). Have been placed. The arrangement pattern of the two-dimensional photonic crystal is not limited to a shape formed using a square, and may be formed using a regular triangle or a regular hexagon. Light whose wavelength matches the lattice spacing of the two-dimensional photonic crystal is amplified by resonance by the two-dimensional photonic crystal. That is, the photonic crystal periodic structure 10 a is arranged so as to define the wavelength of light generated in the active layer 2. As a result, coherent light is surface-emitted from the light emission region on the main surface side surface of the second semiconductor layer 22.

  At this time, the photonic crystal periodic structure 10a is composed of two types of solid materials 11a and 11b, and the refractive indexes of the solid materials 11a and 11b are based on the refractive indexes of the guide layers 3 and 4 and the cladding layers 5 and 6. Is also small. The solid materials 11a and 11b are arranged along the emission direction of the emitted light L1, and are arranged in the ascending order of the refractive index along the direction. Therefore, although the shape of the photonic crystal periodic structure 10a is, for example, a columnar shape or the like in which the cross-sectional shape in the direction perpendicular to the substrate surface is a quadrangle, the refractive index sensed by the light in the laser is inclined. Can be given. Therefore, the light is first-order diffracted more in a specific direction (that is, the direction from the substrate 1 toward the main surface and from the solid material 11a having a lower refractive index toward the solid material 11b having a higher refractive index). The Therefore, the light utilization efficiency of 50% or more can be obtained by using the emitted light L1 emitted in the direction as the surface emission. That is, the light extraction efficiency in the main light emission direction can be increased.

  Next, a method for manufacturing a two-dimensional photonic crystal surface emitting laser will be described. FIG. 2 is a flowchart showing an outline of a method for manufacturing a two-dimensional photonic crystal surface emitting laser. FIG. 3 is a flowchart showing an example of details of the process of forming the photonic crystal periodic structure. FIG. 4 is a schematic diagram of each step before forming the photonic crystal periodic structure in the method of manufacturing the two-dimensional photonic crystal surface emitting laser shown in FIG. FIG. 5 is a schematic diagram of each step of the method for manufacturing the photonic crystal periodic structure shown in FIG. FIG. 6 is a schematic diagram of each step after forming the photonic crystal periodic structure in the method of manufacturing the two-dimensional photonic crystal surface emitting laser shown in FIG. FIG. 7 is a schematic diagram showing a cross section of the photonic crystal periodic structure in a cross section taken along line VII-VII in FIG. A method of manufacturing a two-dimensional photonic crystal surface emitting laser will be described with reference to FIGS. In addition, the semiconductor material, manufacturing technique, etc. which are applied in the manufacturing method demonstrated below are illustrations, and this invention is not limited to this.

  As shown in FIG. 2, first, in step (S100), a substrate 1 such as an n-type GaN substrate is prepared. Next, in the step (S200), the first semiconductor layer 21 is stacked on the surface on the main surface side of the substrate 1. Specifically, for example, a lower clad layer 5 made of n-type AlGaN is laminated, a lower guide layer 3 made of n-type GaN is laminated, an active layer 2 is laminated, and further made of p-type GaN. The upper guide layer 4 is laminated (see FIG. 1). The first semiconductor layer 21 can be laminated by, for example, an epitaxial crystal growth method such as an OMVPE method (Organic Metal Vapor Phase Epitaxy). FIG. 4A is a schematic view of the prepared substrate 1, and FIG. 4B is a schematic view after the first semiconductor layer 21 is laminated on the substrate 1.

  Note that a buffer layer may be stacked just above the surface on the main surface side of the substrate 1, and the first semiconductor layer 21 may be stacked on the buffer layer. If another layer is stacked directly on the substrate, the crystallinity may be deteriorated. However, if the first semiconductor layer is stacked with a buffer layer interposed, the crystallinity of the first semiconductor layer can be increased. Next, in step (S300), two or more kinds of solid materials having different refractive indexes arranged along the emission direction of the emitted light emitted from the two-dimensional photonic crystal surface emitting laser on the surface of the first semiconductor layer. The configured photonic crystal periodic structure 10a is formed. Details of the step (S300) are shown in FIG. Based on each process shown in FIG. 3, the detail of the process of forming the photonic crystal periodic structure 10a is demonstrated.

As shown in FIG. 3, in the step (S310), one solid material is deposited. Specifically, a thin film material such as a P-CVD (Plasma Chemical Vapor Deposition) method is reacted with the surface on the main surface side of the first semiconductor layer 21 (that is, the surface on the main surface side of the upper guide layer 4). By the CVD process for forming a film, for example, a film of SiO ₂ as one solid material can be formed on the entire surface with a thickness of 1000 mm. FIG. 5A is a schematic view after one solid material 11a is formed.

  Next, in step (S320), a resist is applied to the entire surface of the surface of one solid material. FIG. 5B is a schematic view after the resist 31 is applied. Next, in step (S330), cylindrical holes having a diameter of 1000 mm are formed on the resist 31 in a square lattice pattern (that is, two-dimensional) at a pitch of 2000 mm by lithography technology such as EB (Electron Beam) exposure. At each vertex of a square with a side length of 2000 cm). FIG. 5C is a schematic view after the holes 32 are formed.

Next, in the step (S340), another solid material is deposited inside the hole 32. For example, a film of Al ₂ O ₃ as another solid material having a refractive index larger than that of one solid material can be formed with a thickness of 500 mm by a vacuum vapor deposition method such as an EB (electron beam) vapor deposition method. FIG. 5D is a schematic view after another solid material 11b is formed. At this time, as shown in FIG. 7, the other solid material is made so that the thickness of Al ₂ O ₃ as the other solid material 11 b is smaller than the thickness of the resist 31 and does not completely block the hole 32. 11b is formed into a film. Next, in step (S350), the resist 31 is removed with an organic solvent, and lift-off is performed to remove the other solid material 11b that has been deposited in a position other than the position where the hole 32 is formed in the resist 31. FIG. 5E is a schematic view after the resist is removed. The solid materials 11b are arranged in a square lattice at the positions inside the holes 32 formed in the resist 31. The solid material 11b is formed in a disk shape having a diameter of 1000 mm and a thickness of 500 mm on the surface of the solid material 11a.

Next, in step (S360), the exposed one solid material 11a is partially removed using another solid material 11b having a disk shape as a mask. For example, the exposed one solid material 11a can be removed by a dry etching method such as an RIE (Reactive Ion Etching) method using a fluorocarbon (for example, CF ₄ , CHF ₃ or the like) as an active gas. . FIG. 5F is a schematic view after one solid material is partially removed. On the surface of the first semiconductor layer 21, a cylindrical shape having a diameter of 1000 mm in which the solid material 11 a and the solid material 11 b are stacked is arranged in a square lattice shape, and the photonic crystal periodic structure 10 a is formed.

  Returning to FIG. 2, in the next step (S400), the second semiconductor layer is stacked on the surface of the first semiconductor layer so as to embed the photonic crystal periodic structure 10a. For example, the upper cladding layer 6 is laminated on the surface of the first semiconductor layer 21 so as to embed the photonic crystal periodic structure 10a, and the contact layer 7 is further laminated to form the second semiconductor layer 22 ( (See FIG. 1). For example, the second semiconductor layer can be stacked by the OMVPE method. FIG. 6A is a schematic diagram after the second semiconductor layer is stacked. The second semiconductor layer 22 is stacked on the surface of the first semiconductor layer 21, and the photonic crystal periodic structure 10 a composed of the solid materials 11 a and 11 b is embedded by the second semiconductor layer 22.

  As the material of the upper cladding layer 6, p-type AlGaN may be used, but p-type GaN is more preferable. When the upper clad layer 6 is laminated so as to embed the photonic crystal periodic structure 10a, if the upper clad layer 6 is not properly laminated, the top layer of the photonic crystal periodic structure 10a is directly above the surface of the first semiconductor layer 21. The material of the upper cladding layer 6 is laminated with the same thickness. As a result, a cylindrical shape remains, and the surface on the main surface side of the upper clad layer 6 cannot be made flat. If GaN is used as the material of the upper clad layer 6, growth conditions that are likely to spread laterally can be applied when laminated, so that adjustment is made so that the upper clad layer 6 is not laminated on the upper part of the cylinder (that is, the laminated upper clad layer 6 (second semiconductor Adjustment to flatten the upper surface of layer 22) is easier.

  Next, in step (S500), an electrode is formed. The lower electrode 8 is formed on the surface opposite to the main surface side of the substrate 1, and the upper electrode 9 is formed on the main surface side surface of the second semiconductor layer 22 (that is, the main surface side surface of the contact layer 7). Formed (see FIG. 1). FIG. 6B is a schematic view after the electrodes are formed. Finally, in a step (S600), a predetermined dimension is cut out as post-processing, and a two-dimensional photonic crystal surface emitting laser is completed.

  As described above, in this method of manufacturing a two-dimensional photonic crystal surface emitting laser, the photonic crystal periodic structure 10a is composed of solid materials 11a and 11b having different refractive indexes. A refractive index distribution is created by arranging the solid materials 11a and 11b in the ascending order of the refractive index along the emission direction of the outgoing light L1. As a result, a two-dimensional photonic crystal surface emitting laser capable of increasing the light extraction efficiency in the main light emitting direction can be manufactured. According to this manufacturing method, a two-dimensional photonic crystal surface emitting laser can be manufactured by sequentially laminating semiconductor layers on the surface of one side of a single substrate 1, so that the substrate can be formed as in the conventional manufacturing method. There is no need to use a method of bonding them together. Therefore, the manufacturing process can be simplified, and as a result, the manufacturing cost of the two-dimensional photonic crystal surface emitting laser can be reduced.

(Embodiment 2)
FIG. 8 is a flowchart showing another example of the details of the step of forming the photonic crystal periodic structure. FIG. 9 is a schematic diagram of each step of the method for manufacturing the photonic crystal periodic structure shown in FIG. FIG. 10 is a schematic diagram showing a cross section of the photonic crystal periodic structure in a cross section taken along line XX in FIG. In another example of the manufacturing method of the two-dimensional photonic crystal surface emitting laser described with reference to FIGS. 8 to 10, the details of the process of forming the photonic crystal periodic structure 10a are described in the first embodiment. It is different from the manufacturing method.

  Specifically, as shown in FIG. 8, in step (S <b> 321), a resist is applied to the entire surface immediately above the surface of the first semiconductor layer 21. FIG. 9A is a schematic view after the resist 31 is applied. Next, in step (S331), cylindrical holes having a diameter of 1000 mm are formed in a square lattice pattern at a pitch of 2000 mm on the resist by, for example, EB exposure. FIG. 9B is a schematic view after the holes 32 are formed.

Next, in step (S341), a film of SiO ₂ as one solid material is formed in the hole 32 to a thickness of 500 mm, for example, by EB vapor deposition. Subsequently, a film of Al ₂ O ₃ as another solid material having a refractive index larger than that of one solid material is formed with a thickness of 500 mm. FIG. 9C is a schematic view after one solid material 11a and another solid material 11b are formed and laminated. At this time, as shown in FIG. 10, a SiO ₂ film as one solid material 11a is formed on the surface of the first semiconductor layer 21 on the main surface side, and is laminated on the one solid material 11a. A film of Al ₂ O ₃ as another solid material 11b is formed. One solid material 11a and another solid material 11a and the other solid material 11b are stacked so that the thickness of the laminated one is less than the thickness of the resist 31 and does not completely block the hole 32. 11b is formed.

  Next, in the step (S351), the resist is removed with an organic solvent, and lift-off is performed to remove the solid material deposited other than the positions where the holes 32 are formed in the resist. FIG. 9D is a schematic view after the resist is removed. On the surface of the first semiconductor layer 21, a cylindrical shape having a diameter of 1000 mm in which the solid material 11 a and the solid material 11 b are stacked is arranged in a square lattice shape, and the photonic crystal periodic structure 10 a is formed. Note that the steps before and after the step of forming the photonic crystal periodic structure 10a in the manufacturing method of the two-dimensional photonic crystal surface emitting laser of the second embodiment are as described in the first embodiment. The description will not be repeated.

  In another example of the manufacturing method of the two-dimensional photonic crystal surface emitting laser described above, in the step of forming the photonic crystal periodic structure 10 a, the resist 31 is applied to the surface of the first semiconductor layer 21. Solid materials 11a and 11b are stacked inside the formed holes 32 to form a columnar shape, thereby forming a photonic crystal periodic structure 10a. That is, since the etching process for forming the solid material 11a can be omitted as compared with the first embodiment, the manufacturing process of the two-dimensional photonic crystal surface emitting laser can be further simplified.

(Embodiment 3)
In the description of the first embodiment and the second embodiment, an example in which the photonic crystal periodic structure is configured by two types of solid materials 11a and 11b is described. However, the photonic crystal periodic structure is configured by three or more types of solid materials. Is also possible. FIG. 11 is a schematic cross-sectional view showing Modification Example 1 of the configuration of the two-dimensional photonic crystal surface emitting laser. In FIG. 11, the photonic crystal periodic structure 10 b is composed of three kinds of solid materials 11 a, 11 b, and 11 c and is formed so as to be embedded in the upper cladding layer 6. The solid materials 11a, 11b and 11c are arranged in the ascending order of the refractive index along the outgoing direction of the outgoing light L1, thereby creating a refractive index distribution. With this configuration, the refractive index felt by the light in the laser can be tilted, and the emitted light L1 can be made higher intensity light. By using the emitted light L1 as surface emission, a light use efficiency of 50% or more can be obtained. That is, the light extraction efficiency in the main light emission direction can be increased.

As the solid material, besides exemplarily exemplified SiO ₂ and Al ₂ O ₃ , zirconia (ZrO ₂ , refractive index of about 2.19), silicon nitride (Si ₃ N ₄ , refractive index of about 2.02), etc. Can be used. The solid material is preferably as the difference in refractive index from the semiconductor material in which the photonic crystal periodic structure is embedded is larger. Note that if the solid material is a conductor, there is a problem that light does not enter the solid material and the characteristics of the surrounding semiconductor material change. Therefore, the solid material may be a semiconductor or an insulator.

(Embodiment 4)
In the description of the first to third embodiments, an example in which the photonic crystal periodic structure is formed so as to be embedded in the upper cladding layer 6 is described. However, the guide layer 3 other than the upper cladding layer 6 is described. 4 or the cladding layer 5 may be embedded. FIG. 12 is a schematic cross-sectional view showing a second modification of the configuration of the two-dimensional photonic crystal surface emitting laser. In FIG. 12, the photonic crystal periodic structure 10 c composed of two kinds of solid materials 11 a and 11 b having different refractive indexes arranged along the emission direction of the emission light L <b> 1 is embedded in the lower guide layer 3. Is formed. Even with this configuration, since the refractive index felt by the light in the laser can be inclined, the light utilization efficiency of 50% or more can be obtained by using the emitted light L1 as surface emission. That is, the light extraction efficiency in the main light emission direction can be increased.

(Embodiment 5)
In the description from the first embodiment to the fourth embodiment, two or more kinds of solid materials having different refractive indexes are arranged and arranged in ascending order of the refractive index along the emission direction of the emitted light L1 on the upper electrode 9 side. However, it may be arranged in descending order of the refractive index along the direction. FIG. 13 is a schematic cross-sectional view showing a third modification of the configuration of the two-dimensional photonic crystal surface emitting laser. In FIG. 13, the photonic crystal periodic structure 10 d is formed so as to be embedded in the upper cladding layer 6. The solid materials 11a and 11b constituting the photonic crystal periodic structure 10d are arranged on the surface of the first semiconductor layer 21 in the order of a solid material 11b having a higher refractive index and a solid material 11a having a lower refractive index. . That is, two types of solid materials having different refractive indexes are arranged in descending order of the refractive index along the emission direction of the outgoing light L1 emitted from the two-dimensional photonic crystal surface emitting laser.

  Even with this configuration, the photonic crystal periodic structure 10d is made of two or more kinds of solid materials having different refractive indexes, has a refractive index distribution, and can incline the refractive index felt by the light in the laser. it can. Since the solid materials 11b having a higher refractive index are arranged on the lower electrode 8 side, the emitted light L2 on the lower electrode 8 side is emitted as emitted light having a higher intensity. Therefore, in the two-dimensional photonic crystal surface emitting laser of this embodiment, the light utilization efficiency of 50% or more can be obtained by using the emitted light L2 as the surface emission. That is, the light extraction efficiency in the main light emission direction can be increased.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

2 is a schematic cross-sectional view showing a configuration of a two-dimensional photonic crystal surface emitting laser according to Embodiment 1. FIG. It is a flowchart which shows the outline of the manufacturing method of a two-dimensional photonic crystal surface emitting laser. It is a flowchart which shows an example of the detail of the process of forming a photonic crystal periodic structure. FIG. 3 is a schematic diagram of each step before forming a photonic crystal periodic structure in the method of manufacturing the two-dimensional photonic crystal surface emitting laser shown in FIG. 2. It is a schematic diagram of each process of the manufacturing method of the photonic crystal periodic structure shown in FIG. FIG. 3 is a schematic diagram of each step after forming a photonic crystal periodic structure in the method of manufacturing the two-dimensional photonic crystal surface emitting laser shown in FIG. 2. It is a schematic diagram which shows the cross section of the photonic crystal periodic structure in the cross section by the VII-VII line of FIG.5 (d). It is a flowchart which shows the other example of the detail of the process of forming a photonic crystal periodic structure. It is a schematic diagram of each process of the manufacturing method of the photonic crystal periodic structure shown in FIG. It is a schematic diagram which shows the cross section of the photonic crystal periodic structure in the cross section by the XX line of FIG.9 (c). It is a cross-sectional schematic diagram which shows the modification 1 of a structure of a two-dimensional photonic crystal surface emitting laser. It is a cross-sectional schematic diagram which shows the modification 2 of a structure of a two-dimensional photonic crystal surface emitting laser. It is a cross-sectional schematic diagram which shows the modification 3 of a structure of a two-dimensional photonic crystal surface emitting laser. It is a cross-sectional schematic diagram which shows an example of a structure of the conventional two-dimensional photonic crystal surface emitting laser. It is a cross-sectional schematic diagram which shows the other example of a structure of the conventional two-dimensional photonic crystal surface emitting laser.

Explanation of symbols

  1 substrate, 2 active layer, 3 lower guide layer, 4 upper guide layer, 5 lower cladding layer, 6 upper cladding layer, 7 contact layer, 8 lower electrode, 9 upper electrode, 10a, 10b, 10c, 10d photonic crystal period Structure, 11a, 11b, 11c Solid material, 21 First semiconductor layer, 22 Second semiconductor layer, 31 Resist, 32 hole, 101 Substrate, 102 Active layer, 103 Lower guide layer, 104 Upper guide layer, 105 Lower cladding layer , 106 upper cladding layer, 107 contact layer, 108 lower electrode, 109 upper electrode, 110a, 110b photonic crystal periodic structure, L1, L2 emitted light.

Claims (5)

An active layer that emits light by injecting carriers;
A guide layer for confining the emitted light in the active layer;
A cladding layer for injecting the carriers into the active layer,
The active layer is disposed so as to be sandwiched between the guide layer and the clad layer,
In the two-dimensional photonic crystal surface emitting laser, the guide layer or the clad layer includes a two-dimensionally arranged photonic crystal periodic structure.
The photonic crystal periodic structure is composed of two or more kinds of solid materials having different refractive indexes arranged along the emission direction of the emitted light emitted from the two-dimensional photonic crystal surface emitting laser. A two-dimensional photonic crystal surface emitting laser.   2. The two-dimensional photonic crystal surface emitting laser according to claim 1, wherein the two or more kinds of solid materials are arranged in an ascending or descending order of refractive index. A method of manufacturing a two-dimensional photonic crystal surface emitting laser,
Preparing a substrate;
Laminating a first semiconductor layer on the surface of the substrate;
A photonic composed of two or more kinds of solid materials having different refractive indexes arranged along the emission direction of the emitted light emitted from the two-dimensional photonic crystal surface emitting laser on the surface of the first semiconductor layer. Forming a periodic crystal structure;
Laminating a second semiconductor layer on the surface of the first semiconductor layer so as to embed the photonic crystal periodic structure;
A method of manufacturing a two-dimensional photonic crystal surface emitting laser. The step of forming the photonic crystal periodic structure includes:
A step of depositing a single solid material;
Applying a resist on the surface of the one solid material;
Forming a hole in the resist;
Depositing another solid material inside the hole; and
Removing the resist;
The two-dimensional photonic according to claim 3, further comprising a step of partially removing the exposed one solid material using the other solid material remaining at a position inside the hole as a mask. Manufacturing method of crystal surface emitting laser. The step of forming the photonic crystal periodic structure includes:
Applying a resist on the surface of the first semiconductor layer;
Forming a hole in the resist;
Laminating one solid material and another solid material in order inside the hole;
The method for manufacturing a two-dimensional photonic crystal surface emitting laser according to claim 3, comprising a step of removing the resist.

Images